The Effect Of Oil’s Repeated Use On Its Oxidation Characteristics And Fried Food’s Quality Characteristics

The article used soybean oil, sunflower oil and corn oil as test oil,using them for more than20times repeatedly,following the quality of each change(acid value, peroxide value, anisidine value,hydroxy value and using the low field nuclear magnetic resonance to detect T2relaxation time).determining the quality of fired food (used fish bean curd as experimental material) every time. At the same time,extracting the oil from the fried food, analyzing the rule of quality change,comparing with the correspondent frying oil.making analysis of the correlation.The main results are as follows:The acid value of soybean oil, sunflower oil and corn oil(frying oil and extraction of oil from fried food) increased with the increased number of frying.But the growth of three kinds of oil is different.The acid value of soybean oil, sunflower oil increases more and more slowly as the increased number of frying,and the acid value of extraction of oil from fish bean curd fried by soybean oil and sunflower oil increases more and more quickly.When fried for the16th time,the acid value is more than3mg/g,which is ruled by the internationality.Because the corn oil is composed by unique structure and fatty,the acid value of corn oil and extraction of oil changes in the same direction,both of them increase slowly with the increased number of frying. When fried for the20th time,their acid value blows the soybean oil and sunflower oil far. It also blows the standard of our nation.Experiment shows that corn oil is a kind of oil which is suitable for the fried food.The peroxide value of soybean oil,sunflower oil,corn oil are irregular fluctuations according to the increased number of frying.The peroxide value of soybean oil begins to exceed0.25%which ruled by internationality when fried for the third time.The peroxide value of sunflower oil, corn oil reduces irregularly and stays on lower level.The anisidine value and hydroxy value of soybean oil, sunflower oil and corn oil increase with the increased number of frying and have significant differences (P<0.05).With the increased number of frying,the anisidine value and hydroxy value of three kinds of oil rise as the following order:sunflower oil>soybean>oil corn oil.Hardness and chewiness of fish bean curd fried by sunflower oil are maximum,elastic, cohesion and shear force value of fish bean curd fried by corn oil are maximum, the tender degrees is the worst.The experiment shows that we can use the low field nuclear magnetic resonance imager to detect T2relaxation time of repeated fried oil.Using the ratio of impurity peak area to reflect the oxidation changes of oil.It is found that change rule of impurity peak area is the same after the three kinds of oil are repeated used.The impurity peak increases with the increased number of frying.This is the new method for rapid detection of oil oxidation.The acid value,anisidine value,hydroxy value and impurity peak area of soybean oil and corn oil present very significant positive correlation (P<0.01). The peroxide value,acid value,anisidine value,hydroxy value,ratio of impurity peak present very significant negative correlation (P<0.01)...